Process for the production of 2,2-dimethylbutane

ABSTRACT

A PROCESS FOR THE PRODUCTION OF 2,2-DIMETHYLBUTANE FROM N-HEXANE COMPRISING CONACTING SAID N-HEXANE WITH AN INITIATOR, A NAPHTHENE INHIBITOR, AND A CATALYST SYSTEM CONSISTING OF HYDROGEN FLUORIDE AND BORON TRIFLUORIDE AT EFFECTIVE PHASE CONTACTING CONDITIOND WITHIN A TEMPERATURE RANGE OF ABOUT 50* F. TO ABOUT 140* F. AND WHEREIN THE PRECISE REACTION CONDITIONS TO UTILIZE ARE CORRELATED BY AN EMPIRICAL EQUATION TO REALIZE AT LEAST 80 PERCENT OF THE THEORETICALLY POSSIBLE YIELD OF 2,2-DIMETHYLBUTANE.

Jan. 15, 1974 J. P. GIANNETTI E AL 3,785,108

PROCESS FOR THE PRODUCTION OF 2, QDIMETHYLBUTANE Filed Aug. 2, 1972 E N I m E N A R T E N w M I w x L I Y. H w T A E X l M E m H R v E 2 H l w T W 6 5 4 2 l O O O O 0 O O United States Patent 3,786,108 PROCESS FOR THE PRODUCTION OF 2,2-DIMETHYLBUTANE Joseph P. Giannetti, Allison Park, and Howard G. Mc-

Ilvried and Raynor T. Sebulsky, Pittsburgh, Pa., as-

signors to Gulf Research & Development Company,

Pittsburgh, Pa.

Filed Aug. 2, 1972, Ser. No. 277,291 Int. Cl. C07c /28 US. Cl. 260--683.66 10 Claims ABSTRACT OF THE DISCLOSURE A process for the production of 2,2-dimethylbutane from n-hexane comprising contacting said n-hexane with an initiator, a naphthene inhibitor, and a catalyst system consisting of hydrogen fluoride and boron trifluoride at effective phase contacting conditions within a temperature range of about 50 F. to about 140 F. and wherein the precise reaction conditions to utilize are correlated by an empirical equation to realize at least 80 percent of the theoretically possible yield of 2,2-dimethylbutane.

This invention relates to the isomerization of normal hexane utilizing an HF-BF catalyst system. More specifically this invention relates to the isomerization of normal hexane to produce substantially equilibrium yields of 2,2-dimethylbutane.

The use of an HFBF catalyst system for the isomerization of various paraflinic hydrocarbons is known in the prior art. However the prior art processes suffer in obtaining poor yields of the most highly branched isomers, such yields being substantially lower than the thermodynamically possible yields at any given temperature. It has now been found in accordance with the invention that normal hexane can be isomerized to produce 2,2-dirnethylbutane in a yield equal to at least 80 percent, usually -80 percent to 98 percent, of that thermodynamically possible at equilibrium at the temperature of reaction, by isomerizing the normal hexane in the presence of an initiator, a naphthene inhibitor and certain concentrations of HF and BE, under low temperature conditions and eflective phase contacting conditions and wherein the choice of variables within defined ranges is made in accordance with defined empirical equations.

The trend to the reduction and possible elimination of lead from gasolines to help combat air pollution will force the refiner to exclude many low octane hydrocarbon streams from the gasoline pool. These low octane hydrocarbon streams were suitable, regarding octane number, with lead addition; however, without lead, these hydrocarbon streams are so poor in octane number that they are no longer suitable for inclusion in the gasoline pool. To compensate for this, the refiner will find it necessary to include hydrocarbon components in the gasoline pool which have superior octane numbers without lead hexane as possible, and it is known that higher yields of 2,2-dimethylbutane are theoretically possible as the temperature of reaction is reduced. The attached figure is drawn from the combined data provided by Evans, H. D.; Fountain, E. B.; and Ross, W. B.; in Low Temperature Isomerization of Pentanes and Hexanes reprinted in the Proceedings of 27th Midyear Meeting. of API Division of Refining, San Francisco, Calif., May 16, 1962, and The Chemistry of Petroleum Hydrocarbons, B. Brooks, et al., editor, Reinhold Publishing Corporation, New York, volume III, chapter 29, page 29.

Referring to the figure, the normalized weight fraction of 2,2-dimethylbutane increases at equilibrium as the temperature is lowered. The weight fractions of n-hexane and other hexane isomers at equilibrium are also normalized.

The novel process of this invention results in the conversion of normal hexane to produce a weight percent of 2,2-dimethylbutane in the product corresponding to at least percent, usually 80 to 98 percent, of the equilibrium value as predicted from the attached figure in the claimed temperature range of 50 F. to F. These very high theoretical yields of 2,2-dimethylbutane from the isomerization of normal hexane are only achieved, however, when the process conditions and the amounts of initiator and inhibitor are not only maintained within the ranges defined below but in addition the variables must be so chosen as to satisfy the below defined empirical Equation I.

The empirical Equation I is as follows:

Equation I a A D6 2 I {1-e sinh where X-=weight fraction 2,2-dimethylbutane in the product; where product includes only products derived from the n-hexane portion of the feed;

e=the base of the natural system of logarithms;

sinh=hyperbo1ic sine function;

cosh=hyperbolic cosine function;

K =equilibrium constant for n-hexane being converted to the sum of Z-methylpentane, 3-methylpentane and 2,3-dimethylbutane;

K =equilibrium constant for the isomers 2- and 3-methylpentane and 2,3-dimethylbutane going to 2,2-dimethylbutane;

0=time in hours;

k,=rate constant for the conversion of C aliphatic hy drocarbons to other than C products;

( aw ea where k =rate constant for the conversion of n-hexane to the sum of 2- and 3-methylpentanes and 2,3-dimethy1butane; and

k =rate constant for the conversion of 2- and 3-methylpentane and 2,3-dimethylbutanes to 2,2-dimethylbutane.

It has additionally been found that the rate constants k k and k;; can be calculated in accordance with the following equations:

- Equation 11 where T=temperature in degrees Rankin C R.); I=the moles of inhibitor in the charge stock divided by the moles of normal hexane in the charge stock.

Equation III 51.74-51 2 V BCS M and C G C C B In each of the Equations II through 1V above appear the quantities C C C and C Each of these quantities is defined in Equations V-VIII below:

Equation V wherein V is equal to the liquid volume of HF employed and V equals the liquid volume of total hydrocarbons employed.

Equation VI 0 0.0034PBF3 1+0.0034 PJBF where 'P is equal to the partial pressure of BE, in the vapor phase in pounds per square inch absolute.

Equation VII C =1+LI4S where S is the starter or initiator concentration given as mole percent based on the total hydrocarbons in the system.

Equation VIII where H is the horsepower input to the reaction per thousand gallons of reaction mixture.

The above set of equations has been derived from both theoretical and empirical considerations. As noted K and K are equilibrium constants, and such constants can be obtained from handbooks. However, it has also been found that K and K can be calculated from the following equations:

Equation IX 1n K1 29.948 0.0971 0.8415 X 10- 1 Equation X In K; 0.23 0.00771 0.1243 X 10 T where in is the natural logarithm function.

equilibrium concentration for other hexane isomers.

The Equation I given above correlates the important reaction variables for the isomerization of normal hexane to produce 2,2-dimethylbutane, and these variables include: (1) temperature; (2) BE; partial pressure; (3) the hydrogen fluoride to hydrocarbon volumetric ratio; (4) the power input to the system; (5) the inhibitor level when utilizing a naphthene'inhibitor; (6) the initiator level; and (7) the reaction time.

For purposes of model development, the reaction of normal hexane to produce 2,2-dimethylbutane was assumed to occur in the following manner:

Equation XI 2-methylpentane n-hexane 3-Inethylpentane 2, a-dimethyibutane 2, 2-dimethylbutane The following Equation XII represents the assumed course of reaction in calculating the various'rate constants:

Equation XII k1 2-MP 1!! 11-06 3-MP 2,2-DMB k- 2,3-DMB 1G 7 X P x where n-C =normal hexane;

MP=methylpentane;

DMB=dimethylbutane;

P =products other than hydrocarbons having six carbon atoms;

k=reaction rate constant with the subscripts indicative of different reactions and the direction of reaction.

It should be noted that k =k /K and k =k /K It was assumed that all of the reactions of normal hexane to form 2-MP, 3-MP and 2,3-DMB were first ors der reactions. It was also assumed that all C hydrocarbons degrade at te same rate (k to form products other than hydrocarbons having six carbons, i.e. cracked products, disproportionated products, and polymerization products. The reaction rate constant k represents, as shown by Equation XII above, an average of the reaction rate constants for the conversion of normal hexane to 2-MP, 3-MP and 2,3-DMB. Similarly, the reaction rate constant k repreesnts an average of the reaction rate constants for the formation of 2,2-DMB from 2-MP, 3-MP and 2,3-DMB. Despite all of these assumptions, it was quite remarkable that a correlation, as shown in Equation I above, could be developed with an ability to predict the results very close to the actual experimental data observed. This correlation will be shown in the actual working examples to be reported on below.

Referring again more specifically to the process, the proper combination of process and catalyst variables essential to the invention is a reaction initiator concentration, a hydrocarbon to hydrogen fluoride volume ratio, a boron trifluoride partial pressure, a naphthene inhibitor concentration, the degree of phase contacting as represented by an input of energy in the form of horsepower per 1,000 gallons of reaction mixture, the reaction temperature employed, and the contacting time.

The charge stock is, of course, normal hexane and can be obtained from any suitable source, such as molecular sieve extraction, distillation, etc. Refinery streams containing hexane and other parafiinic type hydrocarbons, such as n-pentane, can also be employed. Usually the charge stock contains from 50% to 100%, preferably over 75 weight percent, of n-hexane. Aromatics are undesirable and should be excluded as they are known inhibitors for the isomerization reaction.

It is well known in HF-BF isomerization art to add an initiator to the parafiin charge stock; and the particular type of initiator forms no part of this invention. Without an initiator present, a relatively lengthy period occurs before ultimate conversion and selectivity values are reached. Thus any known initiators for the isomerization of parafiinic hydrocarbons in the presence of an HF-BF catalyst system can be employed. Particularly preferred as initiators are monoolefins having from 3 to carbon atoms per molecule and most particularly the unsaturated analogues of hexane. Monoolefinic streams containing minor amounts of diolefins, less than about five weight percent, can also suitably be employed. Examples of effective initiators include propylene, butene-l, butene-Z, pentene- 1, pentene-2, hexene-l, hexene-Z, hexene-3, heptene-l, octene-l, nonene-l, decene-l and other straight-chain olefins. Also included are the isoolefins such as isobutene; 2- methylbutene-l; Z-methylbutene-Z; Z-methylbutene-l; and any isoolefins having from six to 10 carbon atoms.

As noted, the preferred initiators are the monoolefinic hydrocarbons, and in particular the monoolefinic analogues of normal hexane. Since hexene-l is readily available, it is the preferred initiator to employ. With respect to the monoolefin initiators, a preferred range of initator concentration is from about 0.3 mole percent to about 6.0 mole percent, based upon the amount of total hydrocarbon employed, with the more preferred concentration being from about 1.5 to about 3.5 mole percent.

A naphthene-type inhibitor is employed in this reaction to increase the selectivity of the reaction to the desired 2,2-dimethylbutane. Those with ordinary skill in the art will realize that the HF-BF system is also capable of catalyzing undesirable reactions such as cracking, disproportionation, etc., as well as isomerization, and these reactions can occur to a more or less degree within the process and catalyst variable ranges of the isomerization process. The addition of the naphthene-type inhibitor to the catalyst zone decreases the occurrence of these other reactions, and thus permits the production of yields of 2,2- dimethylbutane which more closely approximate the theoretical yields which are possible. The naphthene inhibitors which can be employed include cyclopentane, cyclohexane, cycloheptane, methylcyclopentane, methylcyclohexane, etc. The preferred of these naphthene-type inhibitors are the C naphthenes such as methylcyclopentame and cyclohexane. The quantity of the naphthene inhibitor to employ is preferably from about 12 to about 35 mole percent of the charge stock. A more preferred range for the inhibitor concentration is from about 15 to about 25 mole percent.

The temperature at which the isomerization reaction is carried out is quite important. The preferred reaction temperatures are in a range from about 50 F. to about 140 F., with the more preferred range being F. to F. Process temperatures below about 50 F. are not desirable because the low reaction rates require uneconomically long contacting time; while temperatures significantly above about F. result in reduced theoretical yields of 2,2-dimethylbutane due to equilibrium limitations and in reduced actual yields due to the increase in side reactions.

Another important parameter in the process of this invention is the degree of phase contacting which is achieved between the normal hexane charge stock and the catalyst system which are immiscible. In a laboratory scale apapparatus, increased mixing is normally denoted by an increase in stirring rate. Such increased stirring rate figures, however, are not directly applicable to a larger scale commercial operation. In scaling up from laboratory scale apparatus, those skilled in the mixing or phase-contacting art recognize that the variable to employ to characterize an equivalent degree of phase contacting in a commercial size operation is energy input which is usually defined in terms of horsepower per 1,000 gallons of reaction mixture. As the energy input increases, the degree of phase contacting will also increase in commercial apparatus designed by those having ordinary skill in this art. A suitable range of power input to achieve desirable phase contacting conditions is a power input of at least 0.1 horsepower per 1,000 gallons of reaction mixture, and the power input is usually at least 0.3 horsepower per 1,000 gallons of reaction mixture. A suitable range of power input is from 0.3 to 50 horsepower per 1,000 gallons of reaction mixture. Higher horsepower inputs can also, of course, be used.

As noted above, the catalyst system for use in the process of this invention is composed of hydrogen fluoride and boron trifluoride. The hydrogen fluoride (I-IF) concentration is best expressed in terms of an HF to hydrocarbon (HC) volume ratio and the BF concentration as a partial pressure. Maintaining the HF/HC volume ratio within certain ranges is highly desirable. Too low a volume ratio is unsuitable as there is too little of the HF catalyst component to permit a suitable degree of reaction while too high a volume ratio is unsuitable as a larger and more costly installation is required to produce a suitable quantity of product. A preferred range is 0.2 to 6.0 HF/HC volume ratio, with a more preferred range being 0.4 to 4.0 HF/HC volume ratio.

The BF partial pressure should be at least 30 p.s.i.a. BF partial pressures below 30 p.s.i.a result in substantial decreases in conversion of the normal hexane. More preferably the minimum partial pressure of BF is at least 50 p.s.i.a. Very high partial pressures of BF;;, such as above 1,000 p.s.i.a., for example, are undesirable as they require more extensive high pressure equipment, and since the eifect of BF partial pressure is not linear, increasing BF partial pressure above a certain limit has relatively little benefit in increasing rate of reaction. The upper limit for BF partial pressure is suitably 700 p.s.i.a., although it is understood higher pressures can be employed.

Time is also an important reaction parameter. Too short contact times, even at the most desirable levels of the other process variables, produces an insufiicient degree of reaction, while too long a time can lead to extensive side reactions as well as being economically unattractive 7 due to the requirement for larger reactor sizes. Thus, contact times that give the desired yield of the 2,2-dimethylbutane (80% of equilibrium) and are economically acceptable should be employed. Suitable reaction times are from 10 minutes to four hours, although usually the reaction time is from 0.5 to 1.5 hours.

The invention will be further described with reference to the following experimental work.

In the experiments to follow, the horsepower per 1,000 gallons of reaction mixture was not actually measured, rather, the stirring rate in a two-liter Hastalloy autoclave was measured, and the power input was determined by calculation. The calculation was made from principles set forth in the book Unit Operations by George Brown, published by John Wiley & Sons, Inc., New York (1950), pages 506-509. The calculation was made as follows:

(1) A Reynolds number was obtained by Equation XIII below:

where D =impe1ler diameter in feet;

p=liquid density in lbs./ft.

=impeller speed, revolutions per second; and ,w=liquid viscosity, lbs./ (ft.) (sec.).

where and ,u represent the absolute viscosities of the HF and hydrocarbon phases respectively, and y and z represent the volume fractions of these phases in the mixture.

(2) The power function (P,,) is then obtained from Figure 477 of the Brown Unit Operations book, utilizing the curve which most closely approximates the system in use. In the case of the examples to follow, curve No. 13 was employed.

(3) The power input was then obtained utilizing Equation XV below:

where =the power function (dimensionless);

p=the liquid density, pounds per cubic foot;

=impeller speed, revolutions per second;

D =impeller diameter in feet;

g =conversion factor, 32.2 (lb. mass) (ft.) per (lb.

force) (secF);

fi=conversion factor, 550 (ft.-lb. force/sec.) per horsepower;

V +V =total volume of liquid in gallons.

The procedure to employ in determining whether any particular set of variables is suitable to obtain the results of this invention, namely a weight percent of 2,2-dimethylbutane in the product of at least percent of the theoretically possible value, at the desired reaction temperature, is as follows:

(1) Find the equilibrium concentration in weight fraction for 2,2-dimethylbutane for a given desired temperature of reaction within the defined range (50 F. to 140 F.) using the attached figure;

(2) Obtain values for K and K from information provided in the attached figure '.or from information in the literature or by utilizing Equations IX and X above; and

(3) Set values for the desired time of reaction, inhibitor concentration, initiator concentration, ratio of volume of HF to volume of hydrocarbon, partial pressure of BF;.,, ang the horsepower input, all in the ranges set forth above; an

. (4) Perform the necessary calculations as indicated by Equation I above. If the calculations show that at least 80 percent of the theoretical yield of 2,2-dimethylbutane can be achieved, then those reaction conditions are suitable and are within the defined invention.

Referring again to the figure, the Equilibrium Concentration, weight fraction for the 2,2-dimethylbutane varies from about 0.45 to about 0.59 for the temperature range 140 F. to 50 F. Similarly, the weight fraction of 2,2-DMB range is from about 0.48 to 0.51 for the temperature range .125 F. to F. In accordance with this invention, equilibrium concentrations of 2,2-DMB from 80 to 98% of that thermodynamically possible can be achieved and thus X in Equation I suitably has a value from 0.36 to 0.58, and preferably has a value from 0.38 to 0.50.

The results presented in the following examples give the total charge to the system including HF, BF normal hexane, methylcyclopentane and hexene-l. The product analysis, however, has been normalized to exclude hexene-l and methylcyclopentane or any products formed from these materials. Thus, the product analysis shows only unconverted normal hexane and products formed from normal hexane during the reaction. These analyses are listed as 2,2-dimethylbutane, normal hexane, other hexane isomers (which includes 2-methylpentane, 3- methylpentane and 2,3-dimethylbutane) and non-C products, which includes all remaining components excluding the olefin initiator and the naphthene inhibitor or its product (methylcyclopentane isomerizes to cyclohexane).

The general experimental procedure was as follows unless indicated otherwise:

A two-liter Hastalloy autoclave equipped with a magnetic stirrer assembly, thermocouple well, cooling coils, and facilities for introducing or withdrawing materials was employed. Except where noted otherwise, the HF was pumped into the autoclave followed by the BF While stirring slowly the temperature was lined out to that desired in the run. Approximately 80 weight percent of the normal hexane to be isomerized, along with the methylcyclopentane inhibitor was introduced. Immediately after this addition was completed, the stirring rate was adjusted to that of the run, and the remainder of the normal hexane, along with the hexene-l initiator, was added as rapidly as possible. Timing for the run was begun when the normal hexane-hexene-l blend addition was begun. Samples were withdrawn at specified time intervals during the course of the run. Component analysis was by gas-liquid chromatography.

At the conclusion of each run the temperature within the autoclave was quickly reduced to 50 F. by circulating coolant through the interior coils and then the reactor was discharged.

A first series of runs was made to show the effect of hexene-l initiator level. The results of these runs are shown in Table I below.

TABLE I Example 1 Example 2 Process conditions:

HF, 315 320 BF: 215 217 n-Hexane, ml 300 300 Methylcyclopentane, ml 45 45 Hexene-l, mole percent based on total hydrocarbon 3 Temperature, F..- 125 125 Time, hrs 1. 25 1. 25 Stirring rate, r.p.m 2, 500 2,500 Additional input for model (Equation HF/total hydrocarbon, vol. ratio .91 .91 Power input, horsepower/1,000 gaL. 12. 6 12. 6 BF; partial pressure, p.s.i.a..-. 500 500 Moles of MOP (methylcyclopentane) inhibitor divided by moles of n-hexane charged 19. 8 19. 8 Equilibrium concentration (wt.

percent) of 2,2-DMB thermodynamically possible from the figure 47. 5 47. 5

A 1 P 1 A 1 P 1 Wt. percent product based on n-hexane charge 2,2-dimethylbutane- 15. 8 15. 7 41. 7 41. 6 Other hexane i sm'nere 57, 7 45, 5 n-Ffexane 25. 9 6. 5 NOD-Cd products 0. 6 6. 3 Percent of thermodynamically possible 2,2-DMB yield actually achieved--." 33.3 33. 1 87. 8 87. 9

1 A=Actual; P=Predicted from Equation 1.

The above results show the benefit of having the hexene-l initiator in that almost a 3-fold increase in the 2,2- dimethylbutane content results from its inclusion. Also, the model accurately predicts the weight percent 2,2-dimethylbutane. The yield of any given product in this application is defined as the weight percent of the product based on the n-hexane charged.

A second series of runs was made to show the effect of the presence of a methylcyclopentane inhibitor. The results of these runs are shown in Table II below.

TABLE II Ex. 3 Ex. 4 Ex. 5

Process conditions:

HF, 315 315 315 BF g 210 220 214 n-Hexane, ml 700 630 560 Methylcyclopentane, ml 40 95 170 Hexened, mole percent on total hydrocarbon 3 3 3 Temperature, F 100 100 100 Time, hrs 2. 75 2. 75 2. 75 Stirring rate, r.p 1, 200 1, 200 1, 200 Additional input for mo 1 (E tion I):

HF/total hydrocarbon, vol.

ratio 42 42 42 Power input, horsepower/1,000

g 83 83 84 B113 partial pressure, p.s.i.a 500 500 500 Moles oi MOP inhibitor divided by moles of n-hexane charged. 8. 9 19.8 38. 5 Equilibrium concentration (wt.

percent) of 2,2-DMB thermodynamically possible from the figure 51. 5 51. 5 51. 5

A P l A 1 P 1 A P 1 Wt. percent based on n-hexane charged:

2,2-dimethylbutane 20. 4 23. 3 34. 2 32. 6 13. 2 11. 7 Other hexane isomers. 23.2 50.1 51.6 n-Hexane 4.2 34.7 Non-Cc products 52. 2 2. 9 0. 5

Percent of thermodynamically possible 2,2-DMB yield actually achieved 39.6 45.2 66.4 63.3 25.6 22.7

1 A =Actual; P =Predicted from Equation I.

Referring to Table II, the results show that if too low a level of methylcyclopentane inhibitor is employed (Example 3), excessive formation of non-C products via hydrocracking, disproportionation, etc., results; while if too much methylcyclopentane is employed (Example 5), the isomerization reaction is too severely retarded. An intermediate level, however, results in the formation of a higher level of 2,2-dimethylbutane. Again, good agreement exists between the experimental results and Equation I above. However, the yield of 2,2-DMB is lower than the desired amount because the other variables are not in the most desired range.

A third series of runs was made to illustrate the effect of temperature. The results of these nuns are shown in Table HI below.

TABLE III Ex. 6 Ex. 4 Ex. 7

Process conditions:

HF, 314 315 315 BF 220 220 203 n-Hexan ml 630 630 630 Methylcyclopentane, ml 95 95 95 Hexene-l, mole percent based on total hydrocarbon 3 3 3 Temperature, F 75 100 125 Time, hrs 2. 75 2. 75 2. 75 Etirriug rate, r.p.m 1, 200 1,200 1, 200 Additional input for model (Equation 1):

HF/total hydrocarbon, vol.

ratio 42 42 42 Power input horsepower/1,000

gal 81 83 85 BF; partial pressure, p.s.i.a 500 500 500 Moles of MOP inhibitor divided by moles of n-hexane charged 19. 8 19. 8 1. 98 Equilibrium concentration (wt.

percent) of 2,2-D MB thermodynamically possible from the figure 51. 5 47. 7

r Pl 1 n 1 i Wt. percent product based on nhexane charged:

2,2-dimethylbutane 18. 9 16. 1 34. 2 82. 6 42. 2 40. 8 Other hexaneisomers. 52.0 50. 1 43.3 n-Hexane Non-C products Percent of thermodynamically possible 2,2-DMB yield actually achieved 31.5 26.8 66.4 63.3 88.5 85.5

I A=Actual; P=Predicted from Equation I,

The results show that higher temperatures favor the formation of 2,2-dimethylbutane; however, at temperatures significantly above 125 B, there is a marked increase in the formation of non-C products from side reactions. Once more, good agreement is obtained between the actual run data and the prediction of the model (Equation 1).

Yet another series of runs was made to show the effect of BF partial pressures. The results of these runs are shown in Table IV below.

TABLE IV Ex. 8 Ex. 4 Ex. 5

Process conditions:

314 315 315 110 220 415 630 630 630 Methylcyclopentane, m1 95 95 Hexene-l, mole percent based on total hydrocarbon 3 3 3 Temperature, F 100 100 Time, hrs- 2. 75 2. 75 2. 75 S tirnng rate, r.p.m 1, 200 1, 200 1, 200 Add1tional input for model (Equation I):

HF/total hydrocarbon, vol.

ratio 42 42 42 Power input, horsepower/1,000

gal 83 83 83 BF partial pressure, p.s.i.a 200 500 950 Moles of MCP inhibitor divided by moles of n-hexane charged" 19. 8 19. 8 19. 8 Equilibrium concentration (wt.

percent) of 2,2-DMB thermodynamically possible irom the figure 51. 5 51.5 51. 5

A P A P A P Wt. percent product based on nhexane charged:

2,2-dimethylbutane 24. 8 20. 9 34. 2 32. 6 39. 7 37. 5 Otherhexaneisomers- 57.4 50.1 46.9 n-Hexane 15. Non-C products 2 Percent of thermodynamically possible 2,2-DMB yield actually achicved 48.1 40.6 66.4 63.3 77. 1

1 A=Actua1; P=Predicted from Equation I.

'low level of BF;, where the differences are larger than 1 1 The results show that after about 500 p.s.i.g. BF pressure, there is only a small increase in 2,2-dimethylbutane yield on increasing the BF pressure. The agreement with the values given by the model are good except for the usual.

TABLE VI Ex. 13 Ex. 14 Ex. 15 ,Ex. 16 Ex. 17

Progress conditions:

H 319 323 328 312 327 BF g 50 47 49 49 54 n-Hexane, ml 82 82 82" 82 Methylcyclopentane, 17 17 17 17 Hexene-1, mole percent ha 3 3 3 3 Temperature, 100 100 100' 100 Time, hrs 1.5 1.5 1.5 1.5 Stirring rate, r.p. 1, 800 1, 200 800 400 Additional ingut for model (Equation I):

HF/total ydrocarbon, vol. ratio 3; 2 3. 2 3.2 3.2 3.2 Power input, horsepower/1,000 gal 21. 8 8. 2 2. 4 0. 7 0. 1 BF3 partial pressure, p.s.i.a 100 100 100 100 100 Moles of MOP inhibitor divided by moles of n-hexane charged 23. 2 23. 2 23.2 23. 2 23.2 Equilibrium concentration (wt. percent) of 2,2-DMB thermodynamically possible from the figure 51. 5 r 51. 5 51. 5 51. 5 51. 5

A P A P A P 11 P A P Wt. percent product based on n-hexane charged: 2,2-dimethylbutane 44. 1 43. 5 4 Other hexane isomers Non-Ca products Percent (at thermodynamically possible 2,2-DMB yield actually ac ieve 1 A=Actual; P=Predicted from Equation 1.

Another series of runs was made to determine the effect of HF to hydrocarbon volume ratios, and the results of these runs are shown in Table V below.

TABLE V Referringto Table VI above, the results show that an increased power input results in improved yields of 2,2-

Ex. 10 Ex. 4 Ex. 11 Ex. 12

Process conditions:

HF, g- 315 315 300 435 BFa, g- 215 220 215 225 n-Hexane, ml 945 630 315 630 Methyloyclopentane, m1 140 95 47 95 Hexene-l, mole percent based on total hydrocarbonggh.-. 3 3 3 3 Temperature, F 100 100 100 100 Time, hrs 2. 75 2. 75 2. 75 2. 75 Stirring rate, r.p.m 1, 200 1, 200 1, 200 1, 200 Additional input for model (Equation 1):

HF/total hydrocarbon, vol. ratio 26 42 85 58 Power input, horsepower/1,000 gal- 53 83 1. 3 76 BFz partial pressure, p.s.i.a 550 500 450 650 Moles of MOP inhibitor divided by moles of n-hexane r-harved 8 19. 8 19. 8 19. 8 Equilibrium concentration (W17. percent of 2,2-DMB thermodynamically possible from the figure: 51. 5 51. 5 51. 5. 51. 5

A P A P 11. .P 11

Wt. percent product based on n-hexane charged:

2,2-dimethylbutane 22. 7 20. 6 34. 2 32. 6 46. 6 Other hexane isomers- 53. 5 50.1 41. ne 22.8 12 Non-0 products 1. 0

Percent of thermodynamically possible 2,2-DMB yield ac tually achieved 44.1 40.0 66

1 A=Actual; P=Predicted from Equation I.

Referring to Table V, the results show that the highest yields of 2,2-dimethylbutane result from the highest ratio 70 of HF to hydrocarbon. Again, agreement with Equation I is excellent.

A series of experiments was then run to determine'the effect of power input on the reaction. These experiments were performed in a different manner from the previous 75 ,dimethylbutane. At power inputs significantly below'this range,-Equation I does not predict as it should, as these lower power inputs do not allow for the hydrocarbon and catalyst phases to contact to any great extent.

Finally, a series of runs were made to show the effect of time. The results of these experiments are shown in Table VII. below.

TABLE VII Ex. 18 Ex. 19 Ex. 4

Process conditions:

F, g 315 315 315 BFa, g.---. 220 220 220 5 n-Hexane, 630 630 630 Methylcyclopentane, ml 95 95 95 Hexene-l, mole percent based total hydrocarbon 3 3 3 Temperature, F 100 100 100 Time, hrs 1. 25 2.25 2. 75 Stirring rate, r.p.m 1,200 1, 200 1, 200 Additional input for model (Equation I):

HF/total hydrocarbon, vol.

ratio 42 42 42 Power input, horsepower/1,000

gal 83 83 83 BFa partial pressure, p.s.i.a-- 500 500 500 Moles of MOP inhibitor divided by moles of nhexane charged. 19. 8 l9. 8 19. 8 Equilibrium concentration (wt.

percent) of 2,2-DMB thermodynamically possible from the figure 51. 5 51. 5 51. 5

l l l A P A P A P Wt. percent product based on n-hexane charged:

2,2-dimethylbutane Other hexane isomers n-Hexane N on-O produets Pergent oiztlfirlxxlngdynaliricallg pfissi e2,- '9 acuay achieved 28.3 27.4 48.7 53.6 66.4 63.3

A=Actnal; P=Predicted from Equation 1.

(a) an initiator from about 0.3 to 6.0 mole percent of an initiator based on the total amount of hydrocarbon employed;

(b) a naphthene inhibitor in an amount from 12 to about 35 mole percent based on the weight of n-hexane; and

(c) a catalyst system composed of (1) BF wherein the BE, partial pressure is above about p.s.i. and (2) HF in such concentration that the HP to hydrocarbon volume ratio is from about 0.2. to about 6.0;

under isomerization reaction conditions including a temperature from 50 F. to 140 F. and intimate phase contacting conditions for a time of from 10 minutes to four hours; and wherein the particular values for each variable above are chosen to satisfy the equation where X weight fraction 2,2-dimethylbutane in the product and has a numerical value of at least of the equilib rium weight fraction of 2,2-dirnethylbutane at the chosen reaction temperature;

e=the base of the natural system of logarithms;

sinh =hyperbolic sine function;

cosh=hyperbolic cosine function;

K equilibrium constant for n-hexane being converted to the sum of Z-methylpentane, 3-methylpentane and 2,3-dimethylbutane;

K =equilibrium constant for the isomers 2- and 3-meth ylpentane and 2,3-dimethylbutane going to 2,2-dimethylbutane;

0=time in hours;

k =rate constant for the conversion of C aliphatic hydrocarbons to other than C products;

awe where k =rate constant for the conversion of n-hexane to the sum of 2- and S-methylpentanes and 2,3-dimethylbutane; and

k =rate constant for the conversion of 2- and 3-methylpentane and 2,3-dimethylbutanes to 2,2-dimethylbutane.

2. A process according to claim 1 wherein the initiator is a monoolefin having from 3 to l0 carbon atoms.

3. A process according to claim 2 wherein the initiator has from 6 to 10 carbon atoms and wherein the initiator concentration is from about 1.5 to about 3.5 mole percent.

4. A process according to claim 3 wherein the naphthene inhibitor is present in from about 5 to about 25 mole percent of the n-hexane.

5. A process according to claim 4 wherein the reaction temperature is from F. to F.

6. A process according to claim 5 wherein the HP to BC volume ratio is from 0.4 to 4.0.

7. A process according to claim 6 wherein the BF partial pressure is from 50 to 700 p.s.i.a.

8. A process according to claim 7 wherein the reaction time is from 0.5 to about 1.5 hours.

9. A process according to claim 8 wherein X has a value from about 0.36 to about 0.58.

10. A process according to claim 8 wherein X has a value from about 0.38 to about 0.50.

References Cited UNITED STATES PATENTS 2,370,118 2/1945 Axe 260-68366 2,446,998 8/1948 Burk 260683.66 2,461,545 2/1949 Hepp 260-683.66 2,461,568 2/ 1949 Richmond 260-683.66 2,461,598 2/ 1949 Gibson 260--683.66 2,470,144 5/1949 Clarke 260683.66

DELBERT E. GANTZ, Primary Examiner G. J. CRASANAKIS, Assistant Examiner Patent Dated January 15, 1974 Inventor) Joseph P. Giannetti and Howard G. McIlyried It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. line 35", after "and" insert Equation IV-; Col. 5, line 9, "repreesnts" should be -represents; Col. line 52,, "2-methylbutene-l" should be 3-methylbutene-l Col. 9, line 25, Table I, 'Example 2 last a line under P (across from "2 ,Z-DMB yield actually achieved") "87.9" should be -87.6 Cols. 11 and 12 Table V, the 5th line under "Process Conditions", "hydrocarbongg" should. be

I --hydrocarbon--; T Cols. 11 and 12 Table V, Example 11, first line under "P (across from "2 ,2-Dimeth ylbutene") V should be 45.0 Cols. 11 and 12, Table V, Example 11, under "P (across from "Non-C5 products") the blank space should have dashes similar to those in the places where no numbers appear.

Signed and sealed this 2nd day of July 1974 (SEAL) Attest:

\- EDWARD M. FLETCHERJR.

Attesting Officer C.MARSHALL DANN Commissioner of Patents 

